Magnetic couplings for imparting simultaneous rotary and longitudinal oscillations

ABSTRACT

Magnetic couplings impart simultaneous reciprocal rotary and longitudinal motions or oscillations to a work element. In preferred embodiments, the magnetic couplings include a drive shaft, an output shaft coaxially aligned with the drive shaft relative to a central axis, and drive and driven magnet assemblies connected operatively to the drive and output shafts, respectively. The drive and driven magnet assemblies include permanent magnets arranged to translate continuous rotation of the drive shaft into simultaneous rotary and longitudinal movements of the driven magnet assembly relative to the drive axis. A resilient support member exhibiting torsional and longitudinal resiliency (e.g., an annular elastomeric disc) is most preferably operatively connected to the output shaft to allow for such simultaneous rotary and longitudinal movements thereof.

FIELD OF THE INVENTION

The present invention relates generally to couplings and methods forimparting simultaneous rotary and longitudinal oscillations to a workpiece, for example, a distal element associated operatively with asurgical instrument. In preferred forms, the present invention isembodied in couplings and methods for surgical instruments (e.g.,ophthalmic microsurgical instruments) so as to achieve relatively highfrequency simultaneous rotary (angular) and longitudinal (linear)oscillations relative to the elongate axis of the surgical instrument'swork piece.

BACKGROUND OF THE INVENTION

During ophthalmic microsurgery, such as lens removal, instruments areused with either horizontal or axial oscillatory movements. Conventionalhorizontal or axial oscillatory instruments using piezoelectrictechnology tend to create heat during surgical procedures which mightcause indirect damage to adjacent ocular tissues.

Recently, U.S. Pat. No. 5,609,602 to Machemer et al (the entire contentof which is expressly incorporated hereinto by reference) disclosed arelatively high frequency rotary oscillatory coupling which includes apair of opposed hubs which are independently rotatable about a commonaxis. Pairs of permanent magnets are provided in the opposed faces ofthe hubs. Thus, when the proximal hub is continuously rotated in aselected rotational direction by a suitable drive motor, the distal hubwill be caused to rotate in that same rotational direction. The distalhub, however, is prevented from rotating a complete rotary cycle andinstead reverses its rotary direction with the assistance of a springmember 30. Thus, the continual reversal of the rotary direction of thedistal hub will cause oscillatory rotary movement to be imparted to adistal element (e.g., associated operatively with a surgicalinstrument).

U.S. Pat. No. 5,717,266 to Maynard, Jr. (the entire content of which isexpressly incorporated hereinto by reference) discloses an oscillatorydrive having a driven rotor that is mounted on a shaft and includesplural driven permanent magnets disposed thereon. A spring arrangementis coupled to the driven rotor and limits both clockwise andcounterclockwise rotation. First and second driving rotors are mountedon the shaft on one and another sides of the driven rotor. The drivemechanism is such that spring-limited oscillatory rotary movementsreciprocally in the clockwise and counterclockwise directions areimparted to the driven rotor. The structures of the Maynard, Jr. '266patent, however, appear incapable of imparting both rotary andlongitudinal oscillations to the driven rotor.

There are a number of prior proposals for imparting simultaneoustorsional and longitudinal oscillations to a medical handpiece tip, asshown in U.S. Pat. No. 4,504,264 to Kelman, U.S. Pat. No. 5,911,699 toAnis et al, U.S. Pat. No. 5,722,945 to Anis et al and U.S. Pat. No.6,077,285 to Boukhny (the entire content of each patent being expresslyincorporated hereinto by reference). IN this regard, the Kelman '264patent discloses a hand-held surgical instrument having a working tipwhich, in addition to longitudinal high frequency vibration, is alsocapable of comparatively low frequency lateral oscillations. The Anis etal '699 and Anis et al '945 patents each disclose a medical handpiecehaving a fragmenting surface formed at a working tip which issimultaneously rotated and reciprocated ultrasonically so that tissue isfragmented. The Boukhny '285 patent discloses a medial handpiece havingtwo sets of piezoelectric elements which are polarized to producelongitudinal and torsional motion.

SUMMARY OF THE INVENTION

Broadly, in one aspect, the present invention is embodied in magneticcouplings which simultaneously impart reciprocal rotary and longitudinalmotions or oscillations to a work element. In preferred embodiments, themagnetic couplings of the present invention are comprised of a driveshaft, an output shaft coaxially aligned with the drive shaft relativeto a central axis, and drive and driven magnet assemblies connectedoperatively to the drive and output shafts, respectively. The drive anddriven magnet assemblies include permanent magnets arranged to translatecontinuous rotation of the drive shaft into simultaneous rotary andlongitudinal movements of the driven magnet assembly relative to thedrive axis. In this regard, the drive magnet assembly most preferablyincludes at least one pair of permanent magnets circumferentiallyspaced-apart and longitudinally staggered relative to one another. Thiscircumferential and longitudinal separation thus cooperatively effectsthe movement of the permanent magnets of the driven magnet assembly tocause movements in both the circumferential and longitudinal directions.Thus, the arrangement of the permanent magnets of the drive magnetassembly is such to create a magnetic “cam” of sorts which affects themovements of the driven magnet assembly.

Most preferably, a resilient support member exhibiting torsional andlongitudinal resiliency (e.g., an annular elastomeric disc) isoperatively connected to the output shaft to allow for such simultaneousrotary and longitudinal movements thereof. In addition, the resilientsupport member establishes limits on the extent of rotary andlongitudinal movements of the driven magnet assembly thereby allowingfor simultaneous reciprocal oscillations in both rotational andlongitudinal directions.

Surgical instruments of the present invention which employ such magneticcouplings will typically include a distal work element which connectedto the driven magnet assembly so as to be capable of reciprocalsimultaneous movements in both rotational and longitudinal directionsrelative to the work element's central axis. Most preferably, therefore,the surgical instrument is hand-held and will include a drive motorwhich is connected operatively to a drive shaft so as to impartcontinuous rotational motion to the drive magnet assembly.

It would also be highly desirable, particularly in the field of surgicalinstruments, if a power supply could be provided to minimize any nettorque and/or vibration on a drive assembly and hence the instrumentitself (e.g., so as to minimize (if not eliminate entirely) noticeablemovements of the surgical instrument that might adversely affect theattending surgeon's manipulation of the instrument). According toanother aspect of the present invention, a power supply which addressessuch a need is also provided.

In this regard, the preferred power supply in accordance with thepresent invention minimizes any net torque and/or vibration produced ona drive assembly. In especially preferred embodiments, the power supplyof the present invention comprises a control circuit which controls theangular velocity of a drive assembly (e.g., the motor and drive magnetassembly) so that its angular velocity is maintained at a constantlevel. Preferably, the control circuit is capable of quickly adjustingthe angular velocity of the drive assembly back to the constant level ifthe rotational speed of drive assembly were to deviate therefrom becauseof, for example, a force load imposed on the drive assembly. Mostpreferably, this adjustment is accomplished in less time as compared tothe time required for one rotation of the drive assembly to thusminimize any net torque and/or vibration thereon.

These and other aspects and advantages will become more apparent aftercareful consideration is given to the following detailed description ofthe preferred exemplary embodiments thereof.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Reference will hereinafter be made to the accompanying drawings, whereinlike reference numerals throughout the various FIGURES denote likestructural elements, and wherein;

FIG. 1 is a perspective view of one particularly preferred embodiment ofa surgical instrument in accordance with the present invention;

FIG. 2 is an exploded perspective view of the principal structuralcomponents employed in the surgical instrument depicted in FIG. 1;

FIG. 3 is an enlarged exploded perspective view of the magnetic couplingassembly in accordance with the present invention;

FIG. 4 is an enlarged cross-sectional elevational view of the couplingassembly in accordance with the present invention;

FIGS. 4A and 4B are each enlarged cross-sectional elevational views of apart of the coupling assembly in accordance with the present inventionand respectively illustrate other possible embodiments of the resilientcoupling that may be used therein;

FIGS. 5-7 are perspective, side elevational and top plan views,respectively, of one possible configuration for a working element thatmay be employed in the surgical instrument of the present invention;

FIGS. 8-10 are perspective, side elevational and top plan views,respectively, of another possible configuration for a working elementthat may be employed in the surgical instrument of the presentinvention;

FIG. 11 is a top plan view of yet another alternative configuration fora working element that may be employed in the surgical instrument of thepresent invention; and

FIG. 12 is a schematic diagram of a preferred power supply circuit thatmay be employed in operative association with the surgical instrument inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A particularly preferred embodiment of a surgical instrument 10 inaccordance with the present invention is depicted in accompanying FIG.1. As shown, the surgical instrument 10 essentially includes a proximalhandle section 12, a distal axially elongate working tool section 14,and a coupling section 16 intermediate of, and coupling, the handle andworking tool sections 12, 14, respectively. Electrical power is suppliedto the instrument 10 via a power cable 18-1 and its associated powersupply 18 (a more detailed description of which appears below). Asuction source 20 is in fluid-communication (via flexible tubing 20-1with the lumen of tube 42 that is within the tool section 14) withworking tip 46-1. This allows biological material to be aspiratedthrough the working tip 46-1 thereof and removed from the operatingfield. Alternatively, of course, the suction source 20 may if desired bereplaced by a fluid source so that the surgical field may be irrigated(e.g., with saline solution) through the tubing 20-1 and then on to thetip 46-1 of the tool section 14.

The various components of the surgical instrument 10 are perhaps moreclearly visible in accompanying FIGS. 2-4. In this regard, the handlesection 12 includes a tubular handle member 22 which threadably receivesan end cap 24 so as to close its proximal end. The interior of thehandle member 22 houses a motor 26 having a rotary drive shaft 26-1extending distally therefrom in coaxial alignment with the longitudinalaxis of the instrument 10. The relative position of the motor 26 withinthe handle member 22 is maintained by a spacer ring 28 positioned withinthe interior of the end cap 24.

A drive hub 30 has a proximal stem 30-1 which is sleeved over the driveshaft 26-1 and is rigidly interconnected thereto by means of a set screw30-2. The drive hub 30 also has a distal retaining cup 30-3 having adistally open end. A drive magnet ring 32 which carries pairs of firstand second permanent magnets 32-1 and 32-2, respectively, is immovablyfixed into the open end of the retaining cup 30-3. A proximal endportion of a bearing pin 34 is also immovably fixed into the proximalstem 30-1 of the drive hub 30. As is seen in FIGS. 2 and 3, the centralaperture 36-1 of the driven magnet assembly 36 is coaxially aligned withthe lumen of the distally located transition tube 38. Thus, the distalend portion of the bearing pin 34 extends coaxially outwardly from theopen end of drive hub 30 through the central aperture 36-1 of the drivenmagnet assembly 36 and is rotatably received within a proximal region ofthe hollow lumen defined by the elongate transition tube 38 (see FIG.4).

The magnet assembly 36 includes a rod-shaped permanent magnet havingexposed arcuately shaped north and south pole faces 36-2 and 36-3,respectively, fixedly embedded within the exterior tubular housing 36-4.The central aperture 36-1 thus extends transversely through therod-shaped permanent magnet and the housing 36-4 in which it isembedded.

A bearing ring assembly 40 is sleeved over the proximal stem 30-1 of thedrive hub 30 so as to facilitate its rotation within the handle member22. Specifically, by virtue of the rigid interconnection between theproximal stem 30-1 and the drive shaft 26-1 of the motor 26, the entiredrive hub 30 will be rotated continuously in a rotational direction.Since the drive magnet ring 32 and the bearing pin 34 are each immovablyfixed to the drive hub 30, they will likewise be rotated in the samerotational direction as the drive hub 30.

The elongate hollow transition tube 38 is rigidly bonded to the housing36-4 of the driven magnet assembly 36 so that the lumen of the tube 38is in coaxial alignment with the central aperture 36-1. As a result, thedriven magnet assembly 36 and the transition tube 38 are moveable as aunit simultaneously in rotary and longitudinal oscillations about andalong, respectively, the central elongate axis of the surgicalinstrument 10 as will be described in greater detail below. During suchrotary and longitudinal oscillations, the driven magnet assembly 36 issupported by the bearing pin 34. In order to dampen vibrations of thedriven magnet assembly 36 (particularly during its reciprocalrectilinear oscillations), an elastomeric washer 30-4 is positionedwithin the drive magnet ring 32 against the base of the retaining cup30-3.

A bushing 39 is immovably fixed to the distal end of the transition tube38. A proximal end of a rigid working tube 42 is, in turn, immovablyfixed to the bushing 39. The proximal end of the bushing 39 isfluid-connected to the terminal end of the flexible tubing 20-1 whichenters the lumen of the transition tube 38 distally of the bearing pin34 via an axially elongate slot 38-1. The tubing 20-1 extends in theproximal direction through an entrance slot 22-1 formed in the handlemember 22 and then on to the suction source 20 (see FIG. 1).

The tool section 14 is generally comprised of a closure hub 44 and anouter rigid working tube 46 immovably fixed to, and thus distallyextends from, the opening 44-1 in hub 44. Thus, the interior workingtube 42 is moveably received within the outer working tube 46 so thatthe latter is sleeved over the former. The proximal flange 44-2 isitself immovably fixed to the distal end of the handle member 22 andincludes an opening 44-3 through which the flexible tubing 20-1 mayextend so as to be fluid-connected with the bushing 39 as describedpreviously. The distal tip of the outer tube 46 includes an opening 46-1which cooperates with the distal tip of the inner tube 42, the purposeof which will be described in greater detail below.

Important to the present invention is the presence of a resilientcoupling between the moveable transition tube 38 and the stationaryclosure hub 44. In the preferred embodiment of this invention depictedin the accompanying drawing FIGS. 1-4, such resilient coupling includesa resilient disc-shaped coupling 50 which allows for both rotary andlongitudinal oscillations of the tube 38 (and hence the interior workingtube 42 immovably fixed thereto). In this regard, the resilient coupling50 most preferably is formed as a one-piece structure from anelastomeric material (e.g., silicone rubber, butyl rubber or the like)and includes an outer flange 50-1 and an inner flange 50-2 which definesan interior cylindrical opening 50-3. As is perhaps more clearly shownin FIG. 4, the proximal end portion of the transition tube 38 isreceived within the interior opening 50-3 and is rigidly bonded theretoby a suitable bonding adhesive. An interior retaining ring 52 iscompressively sleeved over the interior flange 50-2 to ensure that itremains immovably fixed to the transition tube 38. In a similar manner,the outer flange 50-1 is bonded to an interior surface region of theclosure hub 44 by a suitable bonding adhesive. An annular rib 50-1 a isalso provided along with an outer retaining- ring 54 to ensure that theouter flange 50-1 remains immovably fixed to the interior of the closurehub 44. As can be appreciated, the resilient coupling 50 is bothtorsionally and longitudinally resiliently flexible relative to theelongate axis of the surgical instrument 10.

The enlarged exploded view provided by accompanying FIG. 3 provides apictorial representation of the manner in which the magnetic coupling ofthe present invention functions. In this regard, it will be appreciated,of course, that the drive magnet ring 32 is coaxially positioned insurrounding relationship to the driven magnet assembly 36 so that asmall, but meaningful, gap is presented therebetween. In such a manner,the latter is free to move relative to the former.

As is evident from FIG. 3, the magnet pairs 32-1 and 32-2 arelongitudinally off-set relative to one another. Specifically, each ofthe magnets forming the magnet pair 32-1 is disposed in a plane passingtransverse to the elongate axis (A1) of the instrument 10 which isoffset distally a dimension D1 relative to a central transverse plane ofthe magnet ring 32. On the other hand, each of the magnets forming themagnet pair 32-2 is disposed in a transverse plane which is off-setproximally from the central transverse plane of the magnet ring 32 by adimension D2. Thus, the magnet pairs 32-1 and 32-2 are off-set in thelongitudinal direction of axis A1 by the sum of dimensions D1 and D2.

In use, therefore, the magnet ring 32 may be rotated continuously (e.g.,by virtue of the driven interconnection with the drive shaft 26-1 of themotor 26 through the drive hub 30 as described previously) in adirection indicated in FIG. 3 by arrow A2. (Of course, an oppositerotational direction may be imparted to the magnet ring 32, if desired.However, for purpose of discussion, it will be assumed here thatrotation is imparted to the magnet ring 32 in the direction of arrowA2.) The magnetic fields associated with the magnet pairs 32-1 and 32-2will therefore periodically be magnetically coupled and decoupled to thepoles of magnets 36-2, 36-3 of the driven magnet assembly 36. Thus,rotation of the driven magnet assembly 36 in the same direction as arrowA2 will result thereby also rotating the tube 38 and the interiorworking tube 42 operatively attached thereto. Since the resilientcoupling 50 is immovably fixed to both the transition tube 38 and theclosure hub 44, it will exert a resilient torsional force to the drivenmagnet assembly 36 which, at some point during rotation of the drivenmagnet assembly 36, will cause magnetic decoupling to occur with themagnet ring 32. At that time, the driven magnet assembly 36 will thenrotate about the axis A1 in a direction opposite to arrow A2. Of course,continued rotation of the magnet ring 32 about the magnet assembly 36will cause the latter to rotationally oscillate about the axis A1.

Simultaneously with such rotational oscillations, the magnetic forceinteractions between the drive magnet ring 32 and the driven magnetassembly 36 will cause the latter to be moved reciprocallylongitudinally along the axis A1. That is, both simultaneous rotationaland longitudinal oscillations are imparted to the driven magnet assembly36 (and the structures fixed thereto, for example, the transition tube38 and the interior working tube 42) by virtue of the continuousrotational motion of the drive magnet ring 32. Such reciprocallongitudinal oscillations are assured by the longitudinal off-setbetween the magnet pairs 32-1, 32-2 associated with the drive magnetring 32. Thus, the positions of the permanent magnet pairs 32-1, 32-2 inthe drive magnet ring 32 will effectively create a magnetic “cam” thatimparts simultaneous rotary and longitudinal movements relative to theelongate axis A1 of the instrument 10. Moreover, the arrangement of more(or less) magnet pairs, their relative spacing, the arrangement of theirmagnetic poles and/or the rotational speed of the magnet ring 32 willallow those skilled in the art to achieve a wide range of motionprofiles which may be imparted to the working tube 42, for example.

It should be understood that, as used herein and in the accompanyingclaims, the terms “oscillations” and/or “oscillate” mean to movereciprocally between two extreme positions. Thus, in accordance with thepresent invention, those structures which are immovably fixed to thedriven magnet assembly 36 are caused to oscillate simultaneously in bothrotary and longitudinal directions relative to the elongate axis A1.

The resilient elastomeric coupling 50 serves several beneficialfunctions. For example, as described above, the coupling 50 serves tostore energy and release it for very fast movement to the working tube42 in both the axial and rotary directions. In addition, the coupling 50serves to physically seal the proximally located components within thehandle 12 against contamination by foreign matter.

Although the resilient coupling 50 has been shown and described abovewith reference to FIGS. 1-4 as being generally a flat, disc-shaped,unitary elastomeric member, virtually any other geometric design may beemployed satisfactorily to achieve “engineered” movements as may bedesired by the instrument designer. Thus, the disc-shaped resilientcoupling 50 is advantageous in that it provides for more motion in anaxial direction as compared to motion in a rotary direction. However, asshown in accompanying FIGS. 4A and 4B, resilient couplings 50A and 50B,respectively, may be provided with a generally conically-shaped section.It will, of course, be understood that many of the structural componentsdepicted in FIG. 4 are likewise present in the embodiments of FIGS. 4Aand 4B, but have been omitted therein for the purpose of clarity ofpresentation.

As shown in FIG. 4A, for example, a coupling 50A may be providedunitarily with cylindrical base and neck sections 50A-1, 50A-2,respectively, and a generally conically shaped transition section 50A-3.The base and neck sections 50A-1 and 50A-2, may be fixed to the closurehub 44 and transition tube 38 via retaining rings 50A-4 and 50A-5,respectively.

Accompanying FIG. 4B shows another embodiment of a resilient coupling50B that may be employed in the practice of the present invention. Asshown, the coupling 50B has concentrically disposed cylindrical(tubular) inner and outer sections 50B-1, 50B-2, respectively, which areunitarily joined to one another at their distal ends by a generallyconically shaped transition section 50B-3. The cylindrical inner andouter sections are fixed to the transition tube 38 and the closure hub44 by means of retaining rings 50B-4 and 50B-5, respectively.

The general conical shapes of the transition sections 50A-3 and 50B-3 ofthe resilient coupling 50A and 50B thereby allow the instrument designerto impart greater propensity of movement in a rotary direction. Theangle of the conical shape, its cross-section and the durometer of theelastomeric material from which it is made contribute to the ultimatemotions that are achieved. Thus, as the angle of the conical shapeapproaches zero degrees (i.e., a tubular shape), the motion isessentially mostly in a rotary direction. By varying the angle of theconical shape, one may alter desirably the motion imparted to theworking tube 42. Moreover, the diameter (with constant cross-sectionalarea) controls the ratio of torsional to axial stiffness. That is, alarge diameter thin wall tube is stiffer in torsion than a smalldiameter tube with the same cross-sectional wall area. Thus, withinthese parameters, an instrument designer can “engineer” virtually anytype of axial and rotary oscillations that may be desired.

As those in this art can also appreciate, the simultaneous rotary andlongitudinal oscillations achieved by the present invention can beemployed to usefully move a variety of work elements. For example, asshown in FIGS. 5-7, one embodiment of the working tip 14 includes agenerally hemispherically shaped opening 46-1 formed in the outerworking tube 46 which exposes a terminal edge 42-1 of the interiorworking tube 42. In this manner, the edge 42-1 serves as a cutter (i.e.,by virtue of the rotary and longitudinal oscillations imparted theretoby the magnetic coupling described previously) which allows biologicalmaterial to be removed from a patient (e.g., an ocular lens, orvitreous, during ophthalmic surgery) and aspirated through the opening46-1 and the interior lumen of the tube 42 via suction tube 20-1 and itsassociated suction source 20. The edge 42-1 may be sharpened, serratedor provided with an abrasive material as might be needed for particularsurgical procedures.

In FIGS. 8-10, an alternative tip 14 is proposed whereby the opening46-1′ is generally V-shaped. In the embodiment of FIG. 11, the edge42-1′ may be beveled (angled) relative to the axis A1 of the instrument.Suffice it to say, a large number of variations in the working tip 14may be envisioned which take advantage of the rotary and longitudinaloscillations of the interior working tube 42 as described previously.

A particularly preferred embodiment of a power supply 18 which supplieselectrical power to the instrument 10 via power cable 18-1 (see FIG. 1)in accordance with the present invention is depicted in accompanyingFIG. 12. One goal of the power supply 18 is to control the speed of themotor 26. Specifically, the power supply 18 is designed to control theangular velocity (rotational velocity with respect to the longitudinalaxis of the instrument 10) of the rotary drive shaft 26-1, and hence therespective angular velocities of the entire drive hub 30, drive magnetring 32 and bearing pin 34, so that the angular velocity of the driveshaft 26-1 is maintained at a constant level. By maintaining the angularvelocity of the rotary drive shaft 26-1 at a constant level, any nettorque and/or vibration on the instrument 10 may be minimized.

The power supply 18 controls the angular velocity of the rotary draftshaft 26-1 by supplying variable width full voltage pulses to the motor26 to induce a back EMF voltage therefrom. The back EMF voltage from themotor 26 is indicative of the angular velocity of the rotary drive shaft26-1 and is sampled during the time intervals between when the pulsesare supplied by the power supply 18 to the motor 26. That is, when themotor 26 is “coasting” between pulses supplied by the power supply 18,the motor 26 generates a back EMF voltage which is proportional to theangular velocity of the drive shaft 26-1. The sampled back EMF voltageis then ultimately converted to a voltage signal indicative of the backEMF voltage and compared to a set point voltage indicative of apredetermined desired angular velocity of the rotary drive shaft 26-1.If the voltage signal representing the angular velocity of the driveshaft 26-1 is different than the set point voltage, the power supply 18changes the pulsewidth of the full voltage pulses supplied to the motor26 so that the actual angular velocity of the rotary drive shaft 26-1,as reflected by the sampled back EMF voltage, becomes equal to thedesired angular velocity as reflected by the set point voltage.Specifically, the variable width full voltage pulses supplied from thepower supply 18 to the motor 26 is increased/decreased (i.e., the dutycycle is increased/decreased) as the sampled back EMF voltagedecreases/increases relative to the set point voltage so that theangular velocity of the rotary drive shaft 26-1 will converge to thedesired velocity. The angular velocity of the rotary drive shaft 26-1 isthus maintained at a constant desired level. As will be discussed inmore detail below, by maintaining the rotary drive shaft 26-1 at aconstant angular velocity, the power supply 18 will minimize the nettorque and/or vibration on the instrument 10.

As shown in FIG. 12 the power supply 18 essentially includes a sawtoothwaveform generator 200, a buffer 210, an inverter and DC offset circuit220, a NPN-PNP transistor amplifier 230, a FET amplifier 240, a voltagetranslator and buffer 250, a voltage sampler 260, a buffer 270, acomparator 280, a switch network 291 and a capacitor 292. The motor 26is operatively connected to the power supply 18 as shown in FIG. 12.

In the preferred embodiment, the sawtooth waveform generator 200includes a diode 201, a 10K resistor 202, an inverter 203 and a 0.1 μfcapacitor 204. The sawtooth waveform generator 200 generates a constantfrequency sawtooth waveform at approximately 15 khz. Those skilled inthe art will recognize, however, that this frequency can be changedsimply by changing the values of the resistor 202 and the capacitor 204.

The sawtooth waveform from the generator 200 is provided to the buffer210 which is essentially formed by an unity gain opamp 211.Specifically, the sawtooth waveform is provided to the non-invertinginput of the opamp 211. The buffer 210 prevents the sawtooth waveformgenerator 200 from being loaded by any resistance coupled thereto.

The sawtooth waveform output from the buffer 210 is provided to theinverter and DC offset circuit 220 which includes a 1K8 resistor 221, a1K resistor 222, a 6K8 resistor 223 and an opamp 224. While the valuesof the resistor 221 and resistor 222 enable the opamp 224 to produce areduced-amplitude sawtooth waveform, those skilled in the art willappreciate that these resistor values can be varied. The sawtoothwaveform provided to the inverting input of the opamp 224 is invertedand applied with a DC offset. The output of the opamp 224 will thus bean inverted representation of the sawtooth waveform input to the circuit220 imposed on a DC level. The DC level provided on the non-invertinginput of the opamp 224 through the resistor 223 can be varied (as willbe discussed in more detail below) so that the output of the opamp 224can be have a higher or lower DC level.

The signal output from the circuit 220 is provided to the NPN-PNPtransistor amplifier 230 which includes a 100K resistor 231, a 10Kresistor 232, a NPN transistor 233, a 2K7 resistor 234, a PNP transistor235 and a 3K3 resistor 236. The NPN-PNP transistor amplifier 230“squares up” the inverted sawtooth waveform input from the circuit 220.That is, the amplifier 230 amplifies the inverted sawtooth waveform fromthe circuit 220 and has a high enough gain so that the output of theamplifier 230 is a squarewave.

The squarewave output from the amplifier 230 is used to drive the) gateof the FET 240 to turn it on or off. The FET 240 amplifies the inputsquarewave to correspondingly generate variable width full voltagepulses that drive the motor 26. The pulsewidth of the voltage pulses maybe increased/decreased to correspondingly increase/decrease the angularvelocity of the drive shaft 26-1 of the motor 26. When the FET 240 is onand hence when a voltage pulse is being applied to the motor 26, thesource voltage (15 volts in the preferred embodiment), is imposed acrossthe motor 26. When the FET 240 turns off and hence when the motor is“coasting”, a back EMF voltage of the motor 26 is generated at thejunction between the FET 240 and the motor 26 with respect to the 15volt supply. This back EMF voltage of the motor 26 is indicative of theangular velocity of the rotary drive shaft 26-1.

The voltage translator and buffer 250 includes a 1K0 resistor 251, adiode 252, a 6K2 resistor 253, a PNP transistor 254, a 100 resistor 255and a diode 256. When the FET 240 is turned on and a voltage pulse isbeing applied to motor 26, the diode 252 and the resistor 253 provide acompensated signal to the base of the transistor 254 and a voltageacross resistor 255 is limited by the diode 256. When the FET 240 isturned off and the motor 26 is “coasting”, the diode 252 is forwardbiased so that the voltage across the resistor 251 is essentially thesame voltage across the motor 26. The back EMF signal is generated bythe motor 26 and converted to a current proportional to the back EMFvoltage by the resistor 251 during the “coasting” period. This currentflows through the resistor 255 and diode 256 and is converted to avoltage referenced to ground by the resistor 255. This voltage isinsufficient to cause significant current to flow through diode 256.Accordingly, the voltage across the resistor 255 when the FET 240 is offis indicative of the angular velocity of the rotary drive shaft 26-1 ofthe motor 26.

The voltage sampler 260 includes inverters 261, 262, 266, a diode 263, a39K resistor 264, a 680 pf capacitor 265, a CD4066 gate 267, a 3K3resistor 268, a 100K resistor 269 and a 0.1 μf capacitor 2611. Theinverters 261, 262, 266, diode 263, resistor 264 and capacitor 265generate a delayed sampling pulse that is timed so that when the FET 240turns off, the gate 267 is turned on. This enables the capacitor 2611 tobe charged through the resistor 268 to a smoothed voltage proportionalto the angular velocity of the drive shaft 26-1. The resistor 269charges the capacitor 2611 to a voltage limited by the diode 256 whencontinuous power is applied to the motor 26, e.g., when there are nosampling pulses to otherwise charge the capacitor 2611. The voltagesampler 260 preferably samples the voltage proportional to the angularvelocity near the end of the “coasting” interval because the length oftime that the motor 26 is “coasting” varies inversely to the length oftime that the motor is being powered depending on the load on the motor26.

The signal from the voltage sampler 260, i.e., the voltage across thecapacitor 2611, is provided to the buffer 270 which includes a 1Kresistor 271, a 10K resistor 272, a 5K1 resistor 273 and an opamp 274.The buffer 270 amplifies the signal provided to the non-inverting inputof the opamp 274 and provides an output signal which is proportional tothe angular velocity of the drive shaft 26-1.

The output signal from the buffer 270 is provided to a comparator 280which includes an opamp 281, a 1M resistor 282 and a 0.015 μf capacitor283. Specifically, the signal from the buffer 270 is provided to theinverting input terminal of the opamp 281. The non-inverting input ofthe opamp 281 is operatively connected to a switching network 291 whichprovides a set point voltage indicative of a predetermined desiredrotational velocity of the drive shaft 26-1.

The difference between the voltages on the inputs of the opamp 281 isamplified and filtered by the opamp 281, resistor 282 and capacitor 283and applied to the non-inverting input of the opamp 224 of circuit 220through the resistor 223. If a voltage difference exists between theinputs of the comparator 280, the DC offset applied to the opamp 224will be changed such that the output of the opamp 224 has a different DCoffset. This adjusted DC offset is then applied to the NPN-PNPtransistor amplifier 230 which in turn will increase or decrease theduration of the pulsewidth of the voltage pulses provided by the FET 240to the motor 26 (as needed) to ultimately eliminate the differencebetween the actual angular velocity of the drive shaft 26-1 and itsdesired angular velocity as reflected by the set point voltage. Thus,the difference between the voltages compared by opamp 281 willultimately become zero.

If there is thus a difference between the desired angular velocity ofthe drive shaft 26-1 and its actual angular velocity, the DC offsetlevel is changed so that the angular velocity of the drive shaft 26-1 isincreased or decreased to eliminate the difference. An increase/decreasein the DC offset input to the opamp 224 through the resistor 223 willultimately increase/decrease the pulsewidth (i.e., duty cycle) of pulsesprovided to the motor 26 by the FET 240 and hence increase/decrease theangular velocity of the drive shaft 26-1. The DC level provided to theopamp 224, the duty cycle of the FET 240, and the angular velocity ofthe drive shaft 26-1 are therefore directionally proportional. Thevelocity of the motor for a given duty cycle varies inversely with theload.

The sampling frequency and filter time constants of power supply 18 areselected so that the changes in the duty cycle, and hence power to themotor 26 occur more quickly than the time required for a single rotationof the drive shaft 26-1 of the motor 26 to thereby compensate for anycyclic loading imposed on the drive shaft 26-1. This decreases thevibration of the instrument 10.

Accordingly, the voltage translator and buffer 250, voltage sampler 260and buffer 270 effectively sense and provide a voltage indicative of theangular velocity of the drive shaft 26-1. This voltage is then used bythe comparator 280, inverter and DC offset circuit 220 and NPN-PNPtransistor amplifier 230 and FET 240 to essentially provide a negativefeedback control of the speed of the motor 26.

As described in detail above, the magnet ring 32 may be rotatedcontinuously by virtue of the driven interconnection with the driveshaft 26-1 of the motor 26 through the drive hub 30. The magnet forceinteractions between the drive magnet ring 32 and the driven magnetassembly 36 will cause the later to have both simultaneous rotationaland longitudinal oscillations to be imparted to the driven magnetassembly 36 and structures fixed thereto. The moving parts of the motor26, hub 30, elastomeric washer 30-4, pin 34 and drive magnet ring 32 ofthe instrument 10 are coupled tightly so that they can essentially beviewed as a single mass (hereinafter referred to as the “drive”).Working tip 14 contains the driven magnet assembly 36, transition tube38, bushing 39, working tube 42, retaining ring 52 and a portion offlexible tube 20-1 and resilient coupling 50 to the extent that theportions of tube 20-1 and resilient disk 50 move together with theaforementioned components that move together as a single mass, and willhereinafter referred to as the “driven tip assembly”. The instrument 10can thus be viewed to include two main moving masses, the drive and thedriven tip assembly and two forces coupled thereto, the torque caused bythe rotary movement of the drive and the force imposed by the resilientcoupling 50.

The electric power from the power supply 18 will enable the drive torotate, thereby moving the resilient coupling 50 forward. Energy is thusstored in the coupling 50 as the force on the coupling 50 increases.This increased force provided by the coupling 50 tends to slow theangular velocity of the drive. The power supply 18 senses this tendencyof the drive and increases the power applied to the motor 26 (asdiscussed above) in order to maintain a constant angular velocity of thedrive at a desired level. The increased force imposed on the drive bythe coupling 50 is thus opposed and balanced by the force resulting fromthe increased power supplied from the power supply 18 to the motor 26. Anet torque and/or vibration on the instrument 10 can thus be minimized.

When the drive magnet ring 32 and the driven magnet assembly 36decouple, the driven tip assembly starts to turn in the reversedirection and starts to move forward axially. This movement decreasesthe force applied onto the resilient coupling 50 proportionally to thereverse rotation. The drive is therefore relieved of the load imposed bythe coupling 50 and will tend to thus increase its angular velocity.However, the power supply 18 will sense this tendency and quickly (i.e.,at least less than the time required for the drive to rotate once)decrease the electric power to the motor 26. Again, this control by thepower supply 18 will maintain balanced, opposing forces on theinstrument 10 and therefore minimize the net torque and vibrationthereon.

In much the same manner, any external force which will tend to increaseor decrease the angular velocity of the drive (with respect to a statorof the motor 26 or housing of the instrument 10) can be sensed by thepower supply 18 which will respond by quickly (i.e., at least less thanthe time required for the drive to rotate once) changing the power tothe motor 26 to balance the external force. As described above, thischange in power provided to the motor 26 will generate a force thatopposes the external force and thus decrease any vibration causedtherefrom.

In the preferred embodiment illustrated in FIG. 12, the type of NPNtransistor is 2N222, the type of PNP transistors is 2N2907 and the typeof FET is IRFD120. The type of diodes is 1N914, the type of inverters isCD40106 and the type of opamps is LM324. Those skilled in the art willreadily appreciate, however, that suitable replacements are available.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A magnetic coupling comprising: drive and drivenmagnet assemblies having magnetically cooperative permanent magnetswhich magnetically couple said drive and driven magnet assemblies one toanother, said magnetically cooperative permanent magnets being arrangedin such a manner to translate continuous rotation of said drive magnetassembly about a drive axis into simultaneous rotary and longitudinaloscillations of said driven magnet assembly relative to said drive axis,wherein said driven magnet assembly includes at least one permanentdriven magnet, and wherein said drive magnet assembly includes anannular drive ring surrounding said driven magnet assembly whichincludes at least one pair of circumferentially and longitudinallyspaced apart drive magnets.
 2. The magnetic coupling as in claim 1,further comprising a resilient coupling member exhibiting torsional andlongitudinal resiliency which is connected operatively to said drivenmagnet assembly to allow for said simultaneous rotary and longitudinaloscillations thereof.
 3. The magnetic coupling as in claim 2, furthercomprising drive and output shafts coaxially aligned with one anotheralong said drive axis and connected operatively to said drive and drivenmagnet assemblies, respectively.
 4. The magnetic coupling as in claim 3,further comprising a housing for housing said drive and driven magnetassemblies therewith, and an elastomeric disc is connected to andbetween said output shaft and an interior region of said housing.
 5. Themagnetic coupling as in claim 4, wherein said housing includes anannular bearing assembly which supports said drive magnet assembly forrotational movement within said housing.
 6. The magnetic coupling as inclaim 5, wherein said drive magnet assembly includes a drive hub havingone end portion which carries said drive ring and an opposite endportion which is rotatably supported by said annular bearing assembly.7. The magnetic coupling as in claim 6, wherein said output shaft istubular, and wherein said drive hub includes a bearing pin having (i) afirst end which is immovably fixed to said opposite end portion of saiddrive hub and extends outwardly therefrom along said drive axis andthrough said driven magnet assembly, and (ii) a second end portion whichis rotatably received within said tubular output shaft.
 8. The magneticcoupling as in claim 2, wherein said resilient coupling member includesan elastomeric disc.
 9. The magnetic coupling as in claim 2, whereinsaid resilient coupling member includes an elastomeric conically shapedsection.
 10. The magnetic coupling as in claim 9, wherein said resilientcoupling member includes inner and outer tubular sections each joined atdistal end regions thereof to said conically shaped section.
 11. Amagnetic coupling comprising: a drive shaft; an output shaft coaxiallyaligned with said drive shaft relative to a drive axis; drive and drivenmagnet assemblies connected operatively to said drive and output shafts,respectively, and having permanent magnets arranged to translatecontinuous rotation of said drive shaft into simultaneous rotary andlongitudinal movements of said driven magnet assembly relative to saiddrive axis; a resilient support member exhibiting torsional andlongitudinal resiliency which is operatively connected to said outputshaft to allow for said simultaneous rotary and longitudinal movementsthereof; and a housing defining an interior space for housing said driveand output shafts and said drive and driven magnet assemblies, whereinsaid resilient support member includes an elastomeric disc having innerand outer annulus regions connected immovably to said output shaft andsaid housing, respectively.
 12. The magnetic coupling of claim 11,wherein said elastomeric disc is formed of a silicone rubber or butylrubber material.
 13. The magnetic coupling of claim 11, wherein saiddrive magnet assembly includes an annular bearing assembly, a drivering, and a drive hub, wherein said drive hub has one end portion whichcarries said drive ring and an opposite end portion which is rotatablysupported within said housing by said annular bearing assembly.
 14. Themagnetic coupling of claim 13, wherein said output shaft is tubular, andwherein said drive hub includes a bearing pin having (i) a first endwhich is immovably fixed to said opposite end portion of said drive huband extends outwardly therefrom along said drive axis and through saiddriven magnet assembly, and (ii) a second end portion which is rotatablyreceived within said tubular output shaft.
 15. A magnetic couplingcomprising: (i) a driven magnet assembly having at least one drivenmagnet; and (ii) a drive magnet assembly having an annular drive ringcoaxially surrounding said driven magnet assembly, wherein said drivemagnet assembly includes at least one pair of circumferentially andlongitudinally spaced apart drive magnets; wherein (iii) said drivemagnets and said at least one driven magnet being arranged in such amanner to translate continuous rotation of said drive magnet assemblyabout a drive axis into simultaneous rotary and longitudinaloscillations of said driven magnet assembly relative to said drive axis.16. The magnetic coupling of claim 15, further comprising a drive hubhaving one end which is immovably fixed to said annular drive ring sothat said drive hub and said drive ring rotate as a unit about saiddrive axis.
 17. The magnetic coupling of claim 16, wherein said drivehub includes an annular bearing assembly operatively connected toanother end thereof for supporting said drive hub for rotationalmovement in a predetermined direction about said drive axis.
 18. Themagnetic coupling of claim 16 or 17, wherein said driven magnet assemblyincludes a tubular output shaft extending outwardly therefrom along saiddrive axis, and a central aperture coaxially aligned with said lumen,and wherein said drive hub includes a bearing pin having one end fixedto said drive hub and another end movably received within said lumen ofsaid tubular output shaft, said bearing pin extending through saidcentral aperture of said driven magnet assembly between said one andanother ends thereof.
 19. The magnetic coupling of claim 18, furthercomprising a housing defining an interior space for housing said driveand driven magnet assemblies, and a resilient elastomeric disc havinginner and outer annulus regions connected immovably to said output shaftand said housing, respectively, to support said output shaft forsimultaneous reciprocal rotary and longitudinal movements relative tosaid central drive axis.
 20. A magnetic coupling comprising: a driveshaft; an output shaft coaxially aligned with said drive shaft along adrive axis; and magnetic coupling means which magnetically couples saiddrive and output shafts for translating rotary movements of said driveshaft into simultaneous reciprocal rotary and longitudinal movements ofsaid output shaft relative to said drive axis: wherein said magneticcoupling means includes resilient coupling means for resilientlysupporting said output shaft to allow for said simultaneous reciprocalrotary and longitudinal movements thereof, and wherein said resilientcoupling means includes an annular elastomeric support member exhibitingboth torsional and longitudinal resiliency.
 21. The magnetic coupling ofclaim 20, wherein said magnetic coupling means includes a driven magnetassembly rigidly connected to said output shaft, and an annular drivemagnet assembly surrounding said driven magnet assembly and rigidlyconnected to said drive shaft.
 22. The magnetic coupling of claim 21,wherein said driven magnet assembly includes at least one permanentdrive magnet, and wherein said drive magnet assembly includes an annulardrive ring surrounding said driven magnet assembly which includes atleast one pair of circumferentially and longitudinally spaced apartdrive magnets.
 23. A magnetic coupling comprising: (i) a driven magnetassembly having at least one driven magnet; (ii) a drive magnet assemblyhaving an annular drive ring coaxially surrounding said at least onedriven magnet assembly which includes at least one pair ofcircumferentially and longitudinally spaced apart drive magnets; (iii) adrive hub having one end which is immovably fixed to said annular drivering so that said drive hub and said drive ring rotate as a unit about acentral drive axis thereof, wherein (iv) said drive hub includes anannular bearing assembly operatively connected to another end thereoffor supporting said drive hub for rotational movement in a predetermineddirection about said central drive axis.
 24. The magnetic coupling ofclaim 23, wherein said driven magnet assembly includes a tubular outputshaft which defines a lumen and which extends outwardly therefrom alongsaid central drive axis, and a central aperture coaxially aligned withsaid lumen, and wherein said drive hub includes a bearing pin having oneend fixed to said drive hub and another end movably received within saidlumen of said tubular output shaft, said bearing pin extending throughsaid central aperture of said driven magnet assembly between said oneand another ends thereof.
 25. The magnetic coupling of claim 24, furthercomprising a housing defining an interior space for housing said driveand driven magnet assemblies, and an resilient elastomeric disc havinginner and outer annulus regions connected immovably to said output shaftand said housing, respectively, to support said output shaft forsimultaneous reciprocal rotary and longitudinal movements relative tosaid central drive axis.